The present invention relates to a self-ballasted fluorescent lamp including a fluorescent lamp and a ballast circuit for operating the fluorescent lamp.
The self-ballasted fluorescent lamp includes a screw-shell (e.g., an E26-type screw-shell) which is interchangeable with that of an incandescent lamp. Thus, the self-ballasted fluorescent lamp can be screwed Into a socket for the incandescent lamp for its use. The self-ballasted fluorescent lamp has a structure in which the fluorescent lamp and the ballast circuit are integrated.
The self-ballasted fluorescent lamp has superior features, in comparison to the incandescent lamp, in that the self-ballasted fluorescent lamp has about one-third power consumption and about six-fold life span. Therefore, fin recent years, the self-ballasted fluorescent lamp is rapidly coming into wide use as an energy-saving type of a light source instead of the incandescent lamps.
As the ballast circuit of the self-ballasted fluorescent lamp, a high-frequency inverter circuit is generally used in order to make the entire self-ballasted fluorescent lamp small in size and light in weight.
The ballast circuit of the self-ballasted fluorescent lamp includes a printed circuit board and circuit components disposed on the printed circuit board. A positional arrangement of the circuit components on the printed circuit board is determined, in consideration of electrical circuit design, such that the self-ballasted fluorescent lamp can be small in size by effectively utilizing space in a case for containing the ballast circuit.
Japanese Utility Model Publication for Opposition No. 63-4331 discloses an example of a positional arrangement of circuit components. According to Japanese Utility Model Publication for Opposition No. 63-4331, a component having a maximum mounting height among the circuit components is disposed at the center of a printed circuit board. The circuit components having the other mounting height are disposed around the component having the maximum mounting height toward the circumference of the printed circuit board in order of the height of the mounting height of the other components. Thus, a small-sized ballast circuit is realized.
Japanese Utility Model Publication for Opposition No. 63-4331 does not mention that IC components are disposed on the printed circuit board. Accordingly, Japanese Utility Model Publication for Opposition No. 63-4331 does not take into account measures concerning heat for the case where the IC components are used.
An objective of the present invention is to provide a self-ballasted fluorescent lamp which is capable of reducing an adverse heat influence on IC components.
In order to achieve the above-described objective, a self-ballasted fluorescent lamp according to the present invention includes a fluorescent lamp and a ballast circuit for operating the fluorescent lamp, wherein the ballast circuit includes: a printed circuit board, a heat generating component disposed on a first face of the printed circuit board, which generates heat when the fluorescent lamp is operated, and a semiconductor component disposed on a second face opposite to the first face of the printed circuit board, and wherein the semiconductor component is disposed in an area other than an area on the second face corresponding to an area of the first face where the heat generating component is disposed, thereby achieving the above-described objective.
The semiconductor component may be an inverter driving IC included in an inverter circuit for operating the fluorescent lamp.
The inverter circuit may further include a first switching element driven by the inverter driving IC and a second switching element driven by the inverter driving IC, the heat generating component may be disposed in substantially a central area on the printed circuit board, and an area of the printed circuit board where the inverter driving IC is disposed may be located opposite to an area of the printed circuit board where the first and second switching elements are disposed with respect to the area where the heat generating component is disposed.
The inverter circuit may further include a first switching element driven by the inverter driving IC and a second switching element driven by the inverter driving IC, the heat generating component may be disposed on the printed circuit board in an area close to one end of the printed circuit board, the inverter driving IC and the first and second switching elements may be disposed on the printed circuit board in an area close to the other end of the printed circuit board.
The heat generating component may be a magnetic circuit component.
The semiconductor component may be disposed at a distance of at least 10 mm from a tube end in which an electrode of the fluorescent lamp is provided.